Imidazolium salts are well known to be useful as an epoxy resin curing agent. While most of imidazolium salts are solid, JP-A-57-190018 (Patent Document 1) discloses a 2-ethylhexanoate or an acetate of an imidazole compound as an epoxy resin cure accelerator that is liquid at room temperature. Journal of Japan Society of Colour Material, 50 (1), 2-7 (1977) (Non-Patent Document 1) teaches that an imidazole compound salt with an alkylcarboxylic acid or a phosphoric acid is liquid at room temperature and reports epoxy resin curing by the use of the salt. JP-A-48-5900 (Patent Document 2) discloses an epoxy resin composition containing a sulfonate of an imidazole compound as a curing agent or a cure accelerator. U.S. Pat. No. 3,356,645 (Patent Document 3) discloses a carboxylate, a lactate, and a phosphate of an imidazole compound. All the references cited above neither describe nor suggestion conductivity of these salts.
Some of ammonium salts such as imidazolium salts and pyridium salts are known to become a liquid molten salt at or below 100° C., particularly around room temperature and to exhibit high ion conductivity at relatively low temperatures of 200° C. or lower without using water or an organic solvent. Such molten salts have been studied for applicability as an electrolyte of batteries and the like for their characteristic nonvolatility. Known ionic liquids include a number of imidazole salts or pyridine salts having a substituent introduced to their N-position(s) (see Hiroyuki Ohno (ed.), Ionsei Ekitai—Kaihatsu no Saizensen to Mirai—, CMC Publishing Co., Ltd., 28-31 (2003): Non-Patent Document 2).
Watanabe, et al. report protic, room-temperature molten salts in J. Phys. Chem. B., 107 (17), 4024-4030 (2003) (Non-Patent Document 3), Chem. Commun., 938-939 (2003) (Non-Patent Document 4), Proceedings of The 43rd Battery Symposium in Japan, 102-103 (2002) (Non-Patent Document 5), and ibid., 604-605 (2002) (Non-Patent Document 6). The reported protic, room-temperature molten salts are prepared basically using an amine compound with the positions other than the N-position unsubstituted.
Kreuer, et al. report a proton conductor composed of unsubstituted imidazole and sulfuric acid in Electrochimica Acta, Vol. 43, No. 10-11, 1281-1288 (1998) (Non-Patent Document 7). JP-T-2000-517462 (Patent Document 4) discloses a proton conductor containing an acid and a nonaqueous amphoteric material. The imidazole compounds having a substituent at a position other than the 1,3-positions which are disclosed therein are given as a general formula having one substituent at such a position. The description is absent on limitation of the position of the substituent. The imidazole compound actually used in the description is an unsubstituted compound.
Armand et al. (JP-T-2000-508114: Patent Document 5) discloses a proton conductor in liquid form comprising a mixture of an acid addition salt of a nitrogen base and a nitrogen base, wherein the acid of the acid addition salt is a fluorine-based acid. The fluorine-based acid involves cost and environmental concerns in the production. Use of the basic component (nitrogen base) in excess lowers the melting point but reduces heat resistance.    Patent Document 1: JP-A-57-190018    Patent Document 2: JP-A-48-5900    Patent Document 3: U.S. Pat. No. 3,356,645    Patent Document 4: JP-T-2000-517462    Patent Document 5: JP-T-2000-508114    Non-Patent Document 1: Journal of Japan Society of Colour Material, 50 (1), 2-7 (1977)    Non-Patent Document 2: Ionsei Ekitai—Kaihatsu no Saizensen to Mirai—, CMC Publishing Co., Ltd., 28-31 (2003)    Non-Patent Document 3: J. Phys. Chem. B., 107 (17), 4024-4030 (2003)    Non-Patent Document 4: Chem. Commun., 938-939 (2003)    Non-Patent Document 5: Proceedings of The 43rd Battery Symposium in Japan, 102-103 (2002)    Non-Patent Document 6: Proceedings of The 43rd Battery Symposium in Japan, 604-605 (2002)    Non-Patent Document 7: Electrochimica Acta, Vol. 43, No. 10-11, 1281-1288 (1998)